1. Field of the Invention
The present invention concerns a cable including individually insulated conductors surrounded by at least one sheath which is easy to strip without requiring the use of a special stripping tool.
2. Description of the Prior Art
Document FR-A-2 645 358 describes an electrical cable which includes individually insulated conductors and a sheath directly surrounding them and can also include drain wires between the insulated conductors and the sheath. This cable can be stripped using a special cutting tool which prevents damage to the conductors. To this end the sheath has two pairs of ridges delimiting four longitudinal grooves in facing pairs in two parallel cutting planes, each of these planes intersecting the inside surface of the sheath but remaining outside the conductors and the drain wires, if any. Each ridge adjoins one of the grooves directly delimited and defined in this way. The sheath with its two pairs of ridges and grooves has a cross-section inscribed within a square.
The tool for stripping this cable has two articulated jaws received in the grooves of one pair and actuated to cut the sheath in the aforementioned cutting plane. In conjunction with the pairs of ridges and grooves defined on the sheath, this tool minimizes the risk of damaging the conductors.
Document U.S. Pat. No. 4,755,629 describes a cable for high-frequency signals which includes:
two pairs of individually insulated conductors,
a continuous inner sheath around each pair or a split insulative inner sheath having a figure-of-eight or S-shape around both pairs,
a screen around the two individual inner sheaths or the common inner sheath, and
a protective outer sheath.
The respective inner sheaths on the two pairs have the advantage of separating the two pairs from each other. However, this cable is not easy to strip.
The figure-of-eight shape common inner sheath has two tubular portions joined together by a connecting lug in the common axial plane of the two tubular portions and two slots facing in opposite directions. The S-shape sheath also has two tubular portions joined by a slantwise connecting lug on opposite sides of their common axial plane and two slots on opposite sides of this connecting lug.
This figure-of-eight or S-shape inner sheath has the advantage of separating the two pairs from each other to reduce crosstalk between the pairs. The two slots enable the two pairs to be inserted into the existing inner sheath and therefore also direct removal of the pairs from this sheath without requiring any specific stripping operation. On the other hand, fitting pairs into this sheath can move the conductors and, more importantly, the presence of the two slots cannot achieve the correct distance between the screen and the conductors at their level. This results in increased losses and increased attenuation of signals conveyed by the split inner sheath cable as compared with a cable with two inner sheaths the same thickness as the split inner sheath that are not split.
An object of the present invention is to provide a cable that is easy to strip, especially at locations other than the cable ends, without requiring the use of a special cutting tool and having optimum performance in terms of high-frequency transmission.